◦
For example, in the same section, there can be an NEL 2 (assigned to DG 1 and DG 2) and
also a different NEL 2 (assigned to DG 3 and DG 4).
3. Broadcast the changes to all the controllers in the system.
•
If needed you can override the controller ready status.
Table 4.16
NEL configuration options
Name
Details
NEL ID
Select
NEL 1
,
NEL 2
or
NEL 3
. IDs that are already used are not shown.
NEL trip signal #
Select a controller from the list. Controllers that are not in the same section are not shown.
New NEL trip signal(s)
If there are other controllers in the section that the NEL trip signal can be connected to, you can select
these in the
New NEL trip signal
list.
Label
Customisable label for the non-essential load.
INFO
The NEL must be assigned to the controller on the single-line diagram in order for the NEL functions to be visible under the
controller inputs and outputs.
4.7.2 Non-essential load trip (NEL) function
Non-essential load trip (NEL) groups are tripped to protect the busbar against imminent blackout. The NEL can be configured to trip
(that is, disconnect) if over-current, low busbar frequency, overload and/or reactive overload is measured by a controller.
Each non-essential load (NEL) trip is a function with a warning alarm. The trip is active until the measurement that activated the
alarm returns to normal (unless the alarm is latched; then the trip remains active until the latch is reset). The operator can then
reconnect the non-essential load.
For NEL alarms, you can only set the set point and the delay. You cannot assign other alarm actions or use inhibits.
Up to three non-essential loads (NEL) can be defined per controller. The NELs are tripped individually, that is, a trip of NEL 1 does
not directly influence NEL 2 or NEL 3. Inhibits are used to prevent an NEL trip when the breaker to the busbar is open.
The order in which the non-essential loads trip depend on the associated reference value, set point and delay. The convention is to
trip NEL 1 first and NEL 3 last.
The NEL trip relay is activated when one or more of the NEL alarms is activated. It remains active whenever there is at least one
NEL alarm, even if the original NEL alarm is deactivated.
The NEL trips are always active if the controller has power.
INFO
In this description, # represents the
NEL ID
.
DESIGNER'S HANDBOOK 4189340911K UK
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